Reducing interference in submarine cables



Patented Aug. 19, 1930 A NT OFFICE JOSEPH w. MILNOR, e 'MAPL'EWOODLNEWmnsEY} AND CLIFFORD Hi ORAMER, or

LITTLE NECK, PARK, NEW YORK, AssIGNoR'smo THE WESTERN UNION TELEGRAPHooMP on EW YORK; N. Y., A CORPORATION on NEW YORK IREDUCINGIINI'IERFERENQE IN sUBMAnINE cABLEs Application filed January 8,1927. serial No. 159,943.

This invention relates to means for pre-K venting electrical'interference 'insignaling systems, andespecially for preventing a formof interference which arises in telegraph-systems employing oceancables.

It is an ob'ect of the'invention to prevent the deleterious efiectatfthe receiving apparatus of unbalanced disturbing currents arisingwithin the system by reason of the capacitive l relation existing"between' structural parts of the syst m, I

I More particularly, it an objectof-"theinvention to provideneutralization of the" static picked up from the cable-sheath" wi h1n' ashort distance from the cable station. I

", Among "the disturbances affecting a sub: i

induction marine cable are those due to the operation oi electricalsystems in the locality of the landing point of the cable. It has beendetermined experimentallythat the greater part of this disturbance maybe picked up by the cable circuit inthe section of cable adjacent totheoperating station andextending a short the head of the artificial line12 and-the ardistance to sea. 4

The manner in which the cable is aflected by" such disturbance will beexplained in con nection with the attached drawings, in which Figpl isa'schematic drawing showing a conventional duplex; cable circuit withthe in terferenceneutralizingmeans of our inven tion applied thereto;

, Figs. '2 and 3 illustrate two ways which this invention maybe appliedto a simplex circuit; Fig.4 showshow the invention may also be appliedto acable'circuit in which the sea earth-conductoris terminatedin animped ance instead of being connected directly to ground-. t similarparts infallit'he figures;

Fig; 1- shows "diagrammatically the Orditerminal connections forduplexoperation of a 1 cable circuit, wherein" the T6C61V 1I1gapparatu's'R, at station 1, isconnected across the ratio arms, hereinshown as comprising block or bridge condensers 2, 2, and thetransmitting apparatus T is connected, on thefoneside, to the connectingpoint of theratio arms,

and, on the other side, to ground The artificial line 3, which usuallyhas an impedance approximately equal to thecable impedance,

balances the cable circuit withrespect to' thecable station, are,-however,'subject to dis; turblng currents arising by reason of theelectrostatic capacity, which exists betweeneach ofthem andthecablearmour or sheath'S.

These capacities arerepresented;respectively bycondensers 9 and 10,shown in dotted lines on the vdrawing. It is to be understood, however,tha-t"this -representation is purely symbollc s nce such capacityisnormally uniformly distrlbuted throughout the paralleling length fthecable sheath andcable conductors. to a The drawing also sh'ows aneutralizing capacity 11 andres'istance 14, connected between mour ofthe] cable.

dVhen there is any electrical disturbance in the "earth in the localityof the cable 7, the

armour'or sheath 8 is afiected by thisdist'urbance' and tends to cause adisturbing current to flow into the cable and sea earth conductor's'byiway of capacities 9 and 10. Since theimpedanceof the sea earth conductorto ground through 13 isusually low, the disturbing current in thisconductor will mostly flow to ground through the sea earth 13 withoutaffecting the receiving apparatus R. The cable conductor, however, has arelatively high impedance to ground, and since the arti- -ficial line3has animpedance approximately'equal to the cable, impedance, thedisturbing current flowing into the cable conductor willdivideapproximately equally, half of itflowing 'fromthe cablev conductor toground, at sea, and half'flowing back through the receiving'apparatusR,artificial line 3 and sea earth conductor 6 to: ground.

' If a neutralizing capacity 11 and resistance 14 be connected betweenthe head of the artiiicial line12 and the armour or sheath 8 of thecable, a'neutralizing current may be made Jon posite in direction to thedisturbing currentcaused by the capacity 9, thus neutralizing the effect01 the disturbance on the recelvlng apparatus. Capacity 11 will usuallybe approxnnately equal to capacity 9, and resistance 14 will usually below.

Although the neutralizing device has been described above in connectionwith a duplex cable circuit, it will work equally well on a simplexcircuit, i. e., a circuit operated in one direction only. Fig. 2showsthe manner in which this invention may be applied to a simplexcircuit, In this figure capacity and 1 esistance' 16, having animpedance preferably approximately equal to the characteristic cableimpedance, are connected between the sea earthconductor and thereceiving apparatus. Capacity 11 and resistance 14: form theneutralizing circuit and function in the same manner as described inconnection with Fig. 1. 3 e

A second method by which the disturbance may be neutralized on. asimplexcircuit is shown in Fig. 3, in which the cableand sea earthconductors are terminated at points 19 and in a resistance or impedance22, form-. mg one arm or a bridge arrangement, of

which resistance or, impedance 23 forms a second arm, capacity 9 a thirdarm, and the neutralizing circuit composed of capacity 17 and resistance18, the fourth arm. The receiving apparatus is connected acrossthediagonal of the bridge to points 19 and 21. WVith capacity 17andresistance 18 adjusted to the proper values, dependent partly upon theratio of impedances 22 and 28, the potential across impedance 23 causedby the neutralizing current madeto flow through capacity 17 andresistance 18, will be equal and opposite to that across impedance 22caused by the disturbing current flowing through capacity 19. Underthese conditions there will be no disturbing potential between points 19and 21,

and the receiving apparatus will not be af fected.

The invention, as illustrated in Figs. 1, 2 and 3, may also'beapplied'to a cable circuit in which the sea earth conductor isterminated in an impedance 24-. This is indicated in the fragmentaryshowing of F ig. 4:. The manner of connecting the signaling apparatusand the neutralizing condenser and resistance will be apparent fromthe'previous figures; however, a somewhat different adjustment of theneutralizing condenser and resistance would obviously be necessary inthis case.

lVhile all of the above applications of the device have been describedin connection with a cable circuit in which a seaearth is used, it maybe applied with equal success to a cable circuit in which a local earthis used for operation of the cable, with the sea earth conductoreliminated. l 5

-Although this device has been described in connection with theneutralization in cable circuits of disturbances due to the operation ofelectrical systems, it may also be used in reducing the effect of otherextraneous disturbances to which all submarine cables are subjected.

It is to be understood that the invention is not limited to theparticular circuits herein shown and described as various modificationsin details may be made without departing from the spirit of theinvention.

What we claim is:

1. A signaling system comprising a submarine cable, terminal signalingapparatus therefor, a conductor connecting said cable with one terminalof said terminal apparatus, a second conductor connected to the otherter- .minal of said apparatus and extending within the cable sheathparallel to said first conductor to a point at sea and grounded thereat,and means c nnecting'the'Sheath and said other terminal adapted tosupply a potential to neutralize disturbing currents induced tween thesheath and the cable. I i

2. A signaling system comprising a submarine cable, terminal signalingapparatus therefor, a conductor connecting said cable with one terminalof said terminal apparatus,- 7 a second conductor connected to the otherterminal of saidapparatus' and extending within the cable sheathparallelto said firstconductor to a point. at sea and grounded there at,the impedance of said ground connection being substantially zero, and acondenser con-, nectedbetween said sheath and said terminal apparatus. 7

3. The combination with a submarine cable, a receiver, a conductorconnecting said cable with one terminal of said receiver, a ground atsea connected with the other terminal of said receiver through a longcon,- ductor paralleling the cable atits shore end within thev cablesheath, the impedance of said ground connection difiering substantially.from the. impedance of said first conductor, and a condenser in series,with a resist-U ance connected between the sheath and said IGCGIVGIK,

- 41-. A signaling system comprising a submarine cable, terminal.apparatus therefor, a conductor of said cable connected to a terminal ofsaid apparatus, and means adapted to supply a potential to neutralizethe dis'-, turbing currents induced between thesheath and saidconductor, said means connecting the sheath of said cableandsaidapparatus.

5. A signaling system comprising a submarine cable, terminal apparatustherefor,;a conductor of said cable connected to a terminal of saidapparatus, and means adapted to supply a potential to neutralize thedis- ,turbing currents induced between the sheath and said conductor,said means embodying a series-connected capacity and reslstance 0onnectlng the sheath of said cable and said apparatus. I V 7 In testlmonywhereof We afiix oursignatures.

JOSEPH W. MILNOR, CLIFFORD H. ORAMER;

